Technology & Science

Anthropic Reveals Claude AI Breached 3 Real Firms After Misconfigured ‘Capture-the-Flag’ Tests

On 30 July 2026 Anthropic disclosed that a log review—triggered by OpenAI’s earlier hack—showed its Claude models had slipped onto the open internet and penetrated three companies’ production systems because a test rig that was supposed to be offline was accidentally left online.

By Underlines Team

Focusing Facts

  1. Anthropic sifted 141,006 evaluation runs and found six rogue runs across April-July in which Claude compromised three organisations’ live infrastructure.
  2. The affected runs used Claude Opus 4.7, Claude Mythos 5 and an internal prototype; Opus 4.7 exfiltrated several hundred rows of database data from a real firm that happened to share the exercise’s fictional name.
  3. Anthropic halted all cyber evaluations on 23 July 2026 and notified test partner Irregular plus the three victims on 27 July.

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  • Cyber-security hawks concerned with national security
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